With regards to the Me-262, and all others currently flying, none of them come from original airframes. They are all full-scale, very accurate reproductions, which were started by the Texas Airplane Factory and completed by Legend Flyers. Five were built in-all, which included two static (museum display) and three flyers. The Collings Foundation owns/flies one of them (which is based out of Ellington Field), Jerry Yagen/Military Aviation museum owns/flies another (based in Suffolk, VA), and the Messerschmitt Stiftung operates the third (based in Germany). All of these reproductions use the common/abundant CJ610 jet engine (the same as a Learjet). The CJ610's provide a lot more power than what is required, so they never use full-power (however, this also provides some safety margin, by having reserve power if needed). The reproductions were based on re-engineering and using an original two-seat example, WkNr. 110639, as a guide, which was also restored to static display condition, at the same time, and has since been on display at the Naval Aviation Museum Pensacola.
Besides those, there is in-fact an original Me-262 currently in an advanced stage of restoration to airworthy, owned by Paul Allen/Flying Heritage Collection. This aircraft, when completed, will still be remaining about 80% original, and will be powered by newly-built Jumo 004 engines. The aircraft itself, WkNr. 500453, was obtained by the Allies at the end of WWII and sent to the U.S. for evaluation. After the USAAF was done with the aircraft it was passed onto Howard Hughes' company for further research. At the same time, it has been said that Howard Hughes tried to enter the aircraft in the Thompson Trophy race, but was denied from doing so, as the government was entering their P-80 into the race and didn't want the publicity/headlines to come out had the Me-262 won. After Howard Hughes and RKO pictures, the aircraft was obtained by Ed Maloney in 1955 and was displayed at the Planes of Fame Air Museum (Chino) until 2000, when it was purchased by Paul Allen for his Flying Heritage Collection. Over the last fourteen years the aircraft has been under restoration to flying condition and should be the next warbird arriving at the collection, completed and flying. The engines are set to be test-run this month. Although they look identical in appearance, the new-build Jumo 004 engines have been made of modern, higher-strength metals than the originals, and manufactured using modern techniques, with the thought being that they'll be able to get hundreds of hours out of the engines before overhaul (I think the originals were only likely to get to 40-hours max). One can probably only being to imagine the millions of dollars invested in this project!
....and I am grateful for it!
